Shock absorber



Oct. 24, 1967 R. G. POWELL ETAL;

SHOCK ABSORBER 5 Sheets-Sheet 1 Filed July 19,, 1965 J w TA 1 \l E W MV ||.....l|.L w M N Aw w \|l|\ N Sm NM INVENTORS 1967 R. G. POWELL ETAL 3,

SHOCK ABSORBER AGENT 1967 R. e. POWELL ETAL 3, 0

SHOCK ABSORBER Filed July 19, 1965 s sheets-sheet 5 94V AW Y1 26 66 w 10 kHz/$86 FICA/4Z0 6. Po wsu G0ec1 0 Map/11v INVENTORS AGENT United States Patent Ofiice 3,348,703 Patented Oct. 24, 1967 3,348,703 SHOCK ABSORBER Richard G. Powell, Houston, and George D. Moran,

Rosharon, Tex., assignors to ACE Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed July 19, 1965, Ser. No. 473,105 6 Claims. (Cl. 2138) ABSTRACT OF THE DISCLOSURE A hydraulic-pneumatic cushioning unit having inner and outer telescoping cylinder defining a variable volume draft cushioning ohamber therebetween and having a combination bearing and snubbing valve for controlling the extension rate of the cushioning unit subsequent to compression thereof by a bufi force.

This invention is related generally to hydraulic-pneumatic cushion units for minimizing the effects of shock applied to a structure such as a freight car, aircraft landing gear, etc., and more particularly is directed to a novel snubbing construction for controlling the extension rate of the cushion units.

A railway car cushion underframe having a center sill slidable relative to the remainder of the underframe or car structure is well known. A cushion underframe is 1 normally provided with shock absorbing means disposed between a sliding sill structure and a fixed sill structure to cushion or dissipate the energy of impact transmitted from the coupler and sliding sill structure to the car struc ture to protect the lading within the car from damage. Railway cars with cushion undcrfrarnes have become increasingly important in recent years especially because of the increased service speeds of railway freight cars in classifiication yards and the like with a resulting increase in coupler impact between freight cars.

The cushioning or shock absorbing means, such as for example a cushioning unit utilizing a fluid cylinder, is normally positioned intermediate the length of the car between a pair of adjacent of cross bearer members to permit a cushioning means to be easily inserted or re moved and serviced. Shock absorber lug structures are fixed to both the sliding sill and the fixed sill of the railway car and are disposed for contact by the hydraulic cushioning unit in such a manner that impact loads from either end of the car will be absorbed by the hydraulic unit. The interengaging structures between the fixed sill, sliding sill and the hydraulic cushion unit will be described in detail hereinbelow for a better understanding of the invention.

To prevent hydraulic cushioning units from rebounding, i.e., expanding very rapidly and oscillating after an impact force subsides, hydraulic units have been provided with a snubber construction to retard the rate of cushioning unit extension. This snubber construction includes means for controllably metering hydraulic fluid from a snubbing chamber to a storage chamber during the re turn or extension of the hydraulic cushioning unit as it expands from a compressed condition to its initial condition subsequent to the impact load. A check valve structure having a restricted bleed orifice is generally disposed between a hydraulic fluid storage chamber and the snubbing chamber of the hydraulic cushioning unit and is moved away from its checked position during the impact stroke of the unit for allowing substantially unrestricted flow of hydraulic fluid from the storage chamber into the snubbing chamber. During the return stroke, the check valve :moves into its checked position and hydraulic fluid must be forced through the valve restriction, thus retarding the flow of fluid from the snubbing chamber to the storage reservoir and thereby preventing accelerated movement of the hydraulic unit to its extended position.

Additionally, snubber valve arrangements of hydraulic cushion units contribute substantially to the cost of producing the cushioning unit thereby effecting the competitiveness thereof.

Accordingly, it is a primary object of this invention to provide a novel, self-contained, hydraulic-pneumatic cushion unit construction which employs a single integral automatically actuated member for guiding longitudinal relative movement of the telescoping cylinders thereof in addition to controlling the metering of fluid into and out of a snubbing chamber.

his a further object of this invention to provide a novel, self-contained, hydraulic-pneumatic cushioning unit which includes a bearing serving as a snubber valve having a high degree of sliding stability due to its length to dimension ratio, thereby maintaining precise alignment between the inner and outer cylinders of the cushioning unit.

Another object of this invention contemplates the provision of a novel snubber valve bearing structure for a self-contained hydraulic-pneumatic cushion unit which is radially, hydraulically balanced to prevent excessive wear and pressure distortion due to its novel construction.

Briefly, the invention comprises a self-contained, hydraulic-pneumatic cushioning unit having inner and outer cylinders which are spaced to define a snubbing chamber therebetween. A floating piston or follower is disposed within the inner cylinder dividing the same into a variable volume pneumatic chamber and a variable volume inner hydraulic chamber. An orifice cap closes the inner end of the inner cylinder and is provided with a metering orifice. The outer cylinder defines a variable volume outer hydraulic chamber and telescopically receives the inner cylinder. One end of the outer cylinder maintains sealing relation-ship with the outer periphery of the inner cylinder. An end cap forms a closure for the other end of the outer cylinder and retains a metering rod which is adapted to extend through the metering orifice in the orifice cap and controls the effective size of the metering orifice in response to relative positioning of v the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purpose of illustration and description and is shown in the accompanying drawings forming a part of the specification wherein:

FIGURE 1 is a partial sectional view of a freight car underframe in plane. illustrating the employment of a I cushioning unit in a fixed sill sliding sill arrangement.

FIGURES 2 and 3 are views similar to FIGURE 1 illustrating impacting of the cushioning unit respectively from the right and left.

FIGURE 4 is a longitudinal sectional view of the cushioning unit of FIGURE 1 illustrating the cushioning unit in its impacted position at the beginning of its return or extension stroke.

FIGURES 5 and 6 are enlarged partial longitudinal sectional views illustrating positioning of the snubber 3 bearing during the impact and return strokes respectively of the cushion unit of FIGURE 1.

Referring now to the drawings for a better understanding of the invention, in FIGURES l-3 there is illustrated at a fixed sill of a railway car underframe. A sliding sill 12 is disposed Within the fixed sill 10 and is longitudinally moved relative thereto. Generally, the couplers for interconnecting the railway cars to form a train will be fixed one to either end of the sliding sill 12. Opposed sets of cushion lugs 14 and 16 fixed to the sliding sill 12 define a pocket 18 for receiving a self-contained hydraulicpneumatic cushioning unit 20. Opposed sets of cushion lugs 22 and 24 are connected to the fixed sill 10 by welding or the like and are spaced apart a distance equal to the longitudinal spacing of the sliding sill lugs 14 and 16. A pair of cushion keys 26' and 28 are disposed one between each end of the cushioning unit 20 and the cushion lugs of both the sliding sill 12 and the fixed sill 10. The cushion keys 26 and 28 serve to transmit forces from the sliding sill 12 to either of the cushion keys 26 or 28 depending upon the direction of the impact load. The lugs 22 and 24 on the fixed sill 10- serve as support for the cushioning unit 20 and transmit the total load from the cushion unit 20 to the fixed sill 10. To prevent overtravel of the cushion unit upon receiving a severe impact, stop constructions 30 and 32 are connected to the fixed sill 10 and are disposed for contact by the keys 26 and 28, respectively. As illustrated in FIGURE 2, the sliding sill 12 upon being severely impacted from the right will force the right key 28 into engagement with the stops 32 thereby transmitting the entire load of the sliding sill to the fixed sill. The stops 30 and 32 effectively prevent damage to the cushion unit 20, which might occur if a load too great for the unit to withstand is imparted thereto. Until the key 28 contacts the stops 32 the net load transmitted through the cushioning unit will be absorbed by the fixed sill 10 through the support lugs 22 and cushion key 26.

The self-contained hydraulic-pneumatic cushioning unit 20, as illustrated in FIGURE 4, comprises an inner cylinder 34 which is closed at both ends and which is divided into a variable volume inner hydraulic chamber 36 and a variable volume pneumatic chamber 38 by a free-floating piston 40. The piston 40 includes an imperforate diaphragm portion 42 having an annular seal groove 44 formed in the periphery thereof. A mass of suitable sealing material 46 is disposed within the groove 44 and establishes a fluid-tight seal between the piston 40 and the interior cylindrical wall 48 of the inner cylinder 34. The piston 40 has an integral flange or skirt of considerable length having an annular bearing surface 52. at the free extremity thereof for engagement with the cylindrical surface 48 to provide suitable angular stability for the .piston 40 as it reciprocates within the inner cylinder.

The skirt 50 is recessed about its exterior periphery to limit the amount of bearing contact between the skirt 50 and the cylindrical wall 48. The skirt is provided with a series of vent ports 54 to balance the pressure within the recess with the pressure within the inner hydraulic chamber 36. An end cap 56 is fixed in any desired manner, such as by threading, for example, to the inner cylinder 34 forming a closure therefor. The end cap 56 is provided with a valve assembly 58 which allows servicing of the pneumatic chamber 38. Suitable filling equipment may be connected to the valve assembly for the introduction of pneumatic fluid into the pneumatic chamber 38. Although is fitted into a bore formed in the inner cylinder and orifice cap and prevents relative rotation between the orifice cap and inner cylinder to prevent unthreading thereof.

An outer cylinder 66 is fitted about the inner cylinder 34 in telescoping relation thereto. The outer cylinder 66 is provided at one extremity thereof with a packing and bearing chamber in which is positioned a packing adapter 68 and a packing retainer 7 0 which retain dynamic chevron type packings 72 therebetween. The packings 72 are retained under compression by a packing nut 74 which is threadedly received within the outer extremity of the outer cylinder 66. The packing nut- 74 bears against a scraper ring 76 formed of extremely hard material such as a suitable stainless steel for example, and serves to scrape accumulated dirt and other foreign material from the outer periphery of the inner cylinder 34.

An end cap 78 is received within the other extremity of the outer cylinder 66 in any desired manner, for example by threading or the like. A metering pin 80 is threadedly received or otherwise fixed with an aperture formed in the end cap 78 and is adapted to extend through the metering orifice 62 in the orifice cap 60. The metering pin 80 cooperates with the metering orifice 62 to control the flow of hydraulic fluid through the orifice 62 upon compression and extension of the hydraulic cylinder responsive to impact forces to which the cushioning unit is to be subjected.

In accordance with a primary feature of this invention, the orifice cap 60 is provided with an exterior peripheral surface 82 which is slightly smaller than the exterior peripheral surface of the inner cylinder 34 thereby defining a stop shoulder 84 at the extremity of the inner cylinder. An annular retainer ring 86 is fitted within an annular groove 88 formed in the exterior periphery of the orifice cap 60 and serves as a stop for limiting axial movement of a snubber bearing 90 disposed for sliding engagement with the peripheral bearing surface 82. The snubber bearing 90 is provided with an exterior bearing surface 92 of substantial axial dimension which is disposed in sliding bearing engagement with the interior cylindrical surface 94 of the outer cylinder 66. The snubber bearing 90 cooperates with the packing retainer 70 and the packing adapter 68 to maintain a spaced relationship between the inner and outer cylinders 34 and 36, respectively, thereby defining a snubbing chamber 96 therebetween. The snubber bearing 90, the packing retainer and the packing adapter are composed of suitable bearing material. It has been determined, employing specific cylinder materials, that cast iron is an acceptable bearing material. Other suitable bearing materials may be employed with equal effectiveness however.

As illustrated in detail in FIGURES 5 and 6-, the orifice cap is provided with an annular groove or channel 98 formed in the bearing surface 82 which is in communication with the oil chamber 36 by a series of bleed passages 100. The snubber bearing 90 is provided with a series of small metering ports 10-2 and large metering ports 104, which are axially spaced.

A series of longitudinal peripherally spaced passages 106 are formed in the snubber bearing and are disposed in generally parallel relation with the longitudinal axis of the bearing 90. The passages are arranged one intersecting each series of metering ports to establish fluid communication between both the large and small metering ports and the snubbing chamber 96.

The snubber bearing 90 is of less axial length than the distance between the stop shoulder 84 and the retainer member 86 thereby allowing the bearing freedom of axial movement on the bearing surface 82. The small and large metering ports are spaced apart axially sufficiently to allow only one of the metering ports, either large or small, to communicate with the annular groove 98 at any one time. For example, as illustrated in FIGURES 4 and 6, as the cushioning unit 20 begins to expand after being impacted, the snubber bearing 90 will be maintained in intimate contact with the retainer ring 86 by the hydraulic fluid within the snubbing chamber 96 thereby aligning the small metering ports 102 with the annular groove 98 and bleed passages 100 to allow a restricted flow of fluid from the snubbing chamber 96 through the bleed passages 100 to the inner hydraulic chamber 36. The large metering ports 104 will be effectively sealed by the cylindrical bearing surface 82 of the orifice cap 60 under the conditions illustrated in FIGURES 4 and 6. In the compression stroke of the cushioning unit 20', the snubber bearing 90 will be positioned as illustrated in FIGURE 5 with one extremity thereof in abutment with the stop shoulder 84 thereby aligning the large metering ports 104 with the bleed passages 100.

The snubber bearing 90' is reciprocated axially on the bearing surface 82 by the hydraulic pressure differential existing between the inner and outer hydraulic chambers. For example, during compression of the cushioning unit, resulting from an impact force, the hydraulic fluid within the outer hydraulic chamber must be forced through the restricted metering orifice 62 and into the inner hydraulic chamber 36 and the snubbing chamber 96. This causes the pressure within the outer hydraulic chamber to increase causing a pressure differential between the inner and outer hydraulic chambers. The pressure differential will cause the snubber bearing 90 to be pressure actuated (moved axially by the greater force at the axially outer end thereof) into intimate contact with the stop surface 84, thereby aligning the large metering ports 104 with the bleed passages 100. This condition will allow hydraulic fluid to flow from the bleed passages 100 through the large orifices 104 and into the snubbing chamber 96. Axial movement of the snubber bearing at the beginning of the compression and extension strokes of the cushioning unit will be aided by the friction between the snubber bearing and the outer cylinder. This small friction force adds to the hydraulic pressure actuation forces to insure positive rapid movement of the snubber bearing to the proper operative position. The size of the metering ports 104 allows relatively unrestricted flow of hydraulic fluid into the snubbing chambers.

During the extension stroke of the cushioning unit, the snubbing chamber 96 becomes smaller in volume thereby forcing the hydraulic fluid therein outwardly through the bleed passages 100. The volume of the outer hydraulic chamber is increasing at this time thus developing a fluid pressure differential between the snubbing chamber and the outer hydraulic chamber. The pressure differential induces pressure actuation to the snubbing bearing causing the same to move into abutment with the retainer ring 86, thereby aligning the small metering ports 102 with the bleed passages 100. The flow of hydraulic fluid outwardly of the snubbing chamber is thereby retarded by the restricted ports 102 and results in retarding the rate of extension of the cushioning unit.

Operation of the cushioning unit as follows: The normal position of the cushioning unit as it rests within the cushion pocket of the freight car, assuming that the frieght car is neither under buff nor draft and that the sliding sill thereof is centered with respect to the fixed sill, is the position of maximum cushioning unit length hereinafter referred to as the extended position. In the extended position of the cushioning unit 20 as illustrated in FIGURE 1, a maximum impact force on the cushioning unit will force the cushion key members 26 and 28 to abutment with the sliding sill stops 14 and 16 and the fixed sill cushion lugs 22 and 24. In the extended position as illustrated in FIG- URE 1, the cushioning unit will be under minimum internal fluid pressures. For example, in a specific embodiment of the invention it was found that a fluid pressure of 260 p.s.i. was optimum to cause centering of the fixed is connected to the'pneumatic valve assembly ,58 and pneumatic fluid is introduced into the pneumatic chamber 38 until the optimum pneumatic pressure is achieved. The free-floating piston 40 transmits the fluid pressure from the pneumatic chamber 38 to the hydaulic fluid filling the remainder of the cushioning unit. With the cushioning unit 20 in its extended position, the pressure within the inner hydraulic chamber 36 and the outer hydraulic chamber and the snubber chamber will be balanced thereby allowing the snubber bearing 90 to be disposed at any of its positions on the bearing surface 82. Generally, the snubber bearing 90 will be disposed in the position illustrated in the FIGURES 4 and 6 since the last action of the cushioning unit would generally be the extension of a unit from the compressed condition. The free-floating piston 40 in the extended condition of the cushioning unit 20 will be moved by the fluid pressure within the pneumatic chamber 38 to a position adjacent the orifice cap 60 thereby forcing a major portion of the hydraulic fluid into the outer oil chamber. The snubber chamber 96 will be at its condition of minimum volume.

Assuming now that the cushion unit 10' is in the position illustrated in FIGURE 1 and that it is impacted either from the right or the left as illustrated in FIGURES 2 and 3, respectively, the sliding sill 12 through the keys 26 or 28 will cause movement of one end of the cushioning unit in telescoping relationship with the other end thereof. Upon compression of the cushioning unit 20, the hydraulic fluid pressure within the outer chamber will increase to an extremely high pressure range. The metering pin at the beginning of the compression stroke will move within the metering orifice 62 to control the effective aperture size thereof. The metering pin 80, due to its tapered shape, will vary the effective aperture size of the metering orifice 62 from a maximum aperture at the beginning of the compression stroke to a minimum aperture size at the end of the compression stroke. The flow of hydraulic fluid through the metering orifice 62 will, therefore, depend upon the hydraulic pressure within the outer oil chamber and the effective aperture size of the metering orifice 62.

During the compression stroke of the cushioning unit 20, the hydraulic pressure within the outer oil chamber will act upon the outer end snubber bearing thereby causing the snubber bearing to be pressure actuated into abutment with the shoulder 84 on the inner cylinder 34 in the manner described above. This will cause the substantially unrestricted metering ports 104 to be aligned with the bleed passages thereby allowing a substantially unrestricted flow of hydraulic fluid through the passages 100, through the snubber bearing passages 106 into the snubbing chamber 96. Upon compression of the cushioning unit 20, the volume of snubbing chamber 96 will be substantially increased by the telescoping inner and outer cylinders 34 and 66. As the hydraulic fluid under pressure flows from the outer oil chamber'through the orifice 62 and into the inner oil chamber 36, the free-floating piston 40 is forced toward the outer extremity of the inner cylinder 34 thereby compressing the pneumatic fluid within the chamber 38. For example, under conditions of maximum impact, the pneumatic fluid within the pneumatic chamber 38 and thehydraulic fluid within the inner oil chamber 36 may reach a pressure range of 3000 p.s.i. The maximum allowable internal pressure within the inner cylinder 34 and within the outer cylinder 66 will obviously depend upon the specific design characteristics of a particular unit in question, and, therefore, maximum pressure range indicated hereinabove must not be construed as limiting in regard to this invention.

It should therefore be understood that upon compression of the cushioning unit 20 the action of metering the hydraulic fluid from the outer hydraulic chamber into the inner hydraulic chamber and metering fluid from the inner oil chamber to the snubbing chamber and causing compression of the pneumatic fluid within the fluid chamber 38 effectively causes an absorption of a great amount of the impact forces subjected to the sliding sill of a freight car. As illustrated in FIGURES 2 and 3, the cushioning unit 20 is compressed and its internal action is the same regardless of the direction from which it is impacted. With the cushioning unit compressed by movement of the sliding sill either from the right or the left, the sliding sill 12 will be off center with respect to the fixed sill and the cushioning unit 20 will be under extremely high compression. To recenter the sliding sill after the impact force has been dissipated, the pneumatic fluid pressure within the chamber 38 will act on the piston 40 thereby causing the hydraulic fiuid Within the inner chamber 36 to reverse its direction and flow from the inner oil chamber 36 into the outer oil chamber through the metering orifice 62. This causes an expansion of the cushioning unit 20 moving the tapered metering pin 80 outwardly of the metering orifice 62 to thereby increase the effective aperture size of the metering orifice. During the extension movement of the cushioning unit toward its extended position, the free-floating piston 40 will move toward the orifice cap 60 thereby causing an increase in the size of the pneumatic chamber and a decrease in the fluid pressure within the pneumatic chamber thereby varying the pressure within the hydraulic unit from a maximum at its compressed condition to a minimum at its extended position. The flow of fluid through the metering orifice 62 will, therefore, be controlled by the effective size of the metering orifice and the dimensioning pressure within the inner hydraulic chamber 36 and the pneumatic chamber 38.

To prevent an undesirable velocity of cushioning unit extension and movement of the sliding sill towards its centered relationship with the fixed sill, the cushioning unit 20 is provided with means for restricting the flow of hydraulic fluid from the snubbing chamber 96 to the inner hydraulic chamber 36. As the flow of hydraulic fluid through the metering orifice 62 reverses directions at the beginning of the extension stroke, there will occur a pressure drop in the outer hydraulic chamber. Hydraulic fluid acting through the bleed passages 100 and hydraulic fluid from within the snubbing chamber 96 will pressure actuate the snubber bearing 90 into abutment with the retainer ring 86 thereby aligning the small metering ports 102 with the bleed passages 100 and causing the large metering ports 104 to become sealed by the cylindrical bearing surface 82 of the orifice cap 60. Hydraulic fluid from the snubbing chamber 96 flowing through the bleed passages 100 and into the inner oil chamber 36 will thereby be directed through the small metering orifices 102 and will thereby result in a restricted fiow of fluid from the snubbing chamber. During the extensioning stroke of the cushioning unit 20, the snubber bearing 90 will, therefore, restrict the flow of hydraulic fluid from the snubber chamber and thereby prevent rapid extension of the cushioning unit.

To prevent undue radial stressing of the snubber bearing by the substantial fluid pressures developed within the cushioning unit 20, the small and large metering ports 102 and 104, respectively, are formed by drilling bores completely through the snubber bearing. These bores, in effect, cause the pressurized hydraulic fluid within the snubber chamber to be vented through the restricted ports to the bearing surface 82 of the orifice cap and to the inner cylindrical surface 94 of the outer cylinder 66. This construction causes the snubber bearing to by hydraulically balanced in the radial direction by virtue of the construction of the metering ports 102 and 104. Since the snubber bearing 90 may frequently be composed of bearing material-s of considerably less tensile strength than the tensile strength of the orifice cap or the outer cylinder, radial stressing of the bearing material, which could result in damage or improper operation due to overstressing, is effectively prevented.

Another decided advantage in forming the crnetering ports completely through the bearing material lies in the fact that hydraulic fluid from the snubber chamber will aid in lubrication of the bearing surfaces 94 and 82 thereby adding to the effective operating life of the snubber bearing and bearing surfaces.

The snubber bearing, because of its considerable length, also aids in the snubbing action upon extension of the cushioning unit due to its friction with the bearing surface of the outer cylinder 66.

In view of the above, it is readily apparent that we have provided a novel cushioning unit construction which cmploys a minimum number of parts thereby adding to the marketing competitiveness of the invention in addition to providing effective snubbing action to reduce the possibility of cushioning unit rebound. It is also apparent that we have provided a novel cushioning unit construction which employs a bearing member which is effective not only to maintain axial alignment between the inner and outer cylinders of the cushioning unit, but also which is operative to control the extension rate of the cushioning unit. The snubber bearing of our invention effectively aids in the cushioning action upon movement of the cushioning unit to its compressed condition upon impact and aids in the retarding of cushioning unit movement toward its extended position upon the release of the impact force. The novel construction of the snubber bearing in accordance with this invention effectively promotes the lubrication between the snubber bearing and the bearing surface of the orifice cap and the bearing surface of the outer cylinder. The novel construction of the snubber bearing of this invention also promotes hydraulic balancing of the snubber bearing to eliminate any tendency thereof to become damaged due to radial overstressing. It is evident therefore that this invention is one Well adapted to contain all of the objects hereinabove set forth together with other advantages which are obvious and inherent from the description of the apparatus itself.

It will be understood that certain features and sub combinations are of utility and may be employed Without reference to other features and subcombinations.

This is contemplated by and is within the scope of the claims. As many possible embodiments can be made of the invention without departing from the spirit or scope thereof, it is to be understood that all matter hereinabove set forth are as shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What we claim is:

. 1. A hydraulic-pneumatic cushion unit comprising inner and outer telescoped cylinders defining an outer variable hydraulic chamber, said cylinders defining a snubbing chamber therebetween, the inner cylinder being closed at each end thereof, a floating piston disposed within the inner cylinder and dividing the same into a pneumatic chamber and an inner hydraulic chamber, a compressible fluid filling the pneumatic chamber and an incompressible fluid filling the inner hydraulic chamber, the outer hydraulic chamber and the snubbing chamber, one end of the inner cylinder having a metering orifice, the outer cylinder being closed at one end thereof, a metering pin carried by the closed end of the outer cylinder and adapted to extend through the metering orifice to control the size of the same, said inner cylinder having means defining a bearing surface having a bearing stop at either end thereof, a snubber bearing slidably received on the bearing surface and being in bearing engagement with the outer cylinder, bleed passage means in said inner cylinder establishing fluid communication between the hydraulic chamber and the snubbing chamber, the snubber bearing having a plurality of different sized orifices therein, each which communicates with said bleed passage at different positions of said snubber bearing relative to said bearing surface to allow a predetermined rate of hydraulic fluid flow in one direction through the fluid communication, and a lesser rate of fluid flow in the opposite direction, said snubber bearing being hydrostatically balanced to prevent radial stressing of the same by the hydraulic fluid.

2. A hydraulic-pneumatic cushion unit comprising inner and outer telescoped cylinders defining an outer variable hydraulic chamber, said cylinder defining a snubbing chamber therebetween, the inner cylinder being closed at each end thereof, a floating piston disposed within the inner cylinder and dividing the same into a pneumatic chamber and an inner hydraulic chamber, a compressible fluid filling the pneumatic chamber and an incompressible fluid filling the inner hydraulic chamber, the outer hydraulic chamber and the snubbing chamber, one end of the inner cylinder having a metering orifice, the outer cylinder being closed at one end thereof, a metering pin carried by the closed end of the outer cylinder and adapted to extend through the metering orifice to control the size of the same, said inner cylinder having means defining a bearing surface having a bearing stop at either end thereof, an integral snubber valve and snubber bearing slidably received on the bearing surface and being in bearing engagement with the outer cylinder, said inner cylinder having at least one bleed passage formed therein establishing fluid communications between the hydraulic chamber and the snubbing chamber, the snubber bearing having at least one pair of axially spaced ports of different size adapted for alignment on at a time with the bleed passage for allowing a predetermined rate of hydraulic fluid flow in one direction through the bleed passage, and a lesser rate of fluid flow in the opposite direction, whereby extension of said cushion unit is retarded to prevent rebound.

3. In a railway car having a cushioned underframe, a self-contained hydraulic-pneumatic cushioning unit comprising an inner cylinder being closed at both of its ends and having a metering orifice for-med in one of the closed ends, an outer cylinder telescopically and slidably receiving the inner cylinder and having one closed end, said inner and outer cylinders defining a snubber chamber, a metering pin fixed to the closed end of the outer cylinder and extending through said metering orifice, the other end of the outer cylinder including means sealingly engaging the inner cylinder, means defining a bearing surface on said inner cylinder having a bearing stop at either end thereof, bearing means slidably engaging said bearing surface and being in bearing engagement with the outer cylinder, at least one bleed passage formed in the end of the inner cylinder and Opening at the bearing surface, said bearing having a plurality of different sized metering orifices formed therein, said bearing being automatically movable by said hydraulic fluid to a position aligning the larger of said metering orifices with said bleed passage upon compression of said cushioning unit to allow a relatively unrestricted rate of fluid flow into said snubber chamber, said bearing being movable to a position aligning the smaller of said metering orifices with said bleed passage during extension of said cushioning unit to allow a relatively restricted rate of fluid flow out of said snubber chamber to control the rate of extension of said cushioning unit.

4. A self-contained hydraulic-pneumatic cushioning unit comprising an outer cylinder having an end cap closing one end thereof, a metering pin fixed to the end cap and extending along the axis of the cylinder, an inner cylinder received in concentric spaced relation within the outer cylinder and defining a snubbing chamber therebetween, the other end of the outer cylinder being in sealing relation with the inner cylinder, an orifice cap closing the inner end of the inner cylinder and having a metering orifice formed centrally thereof and adapted to receive the metering pin for varying the size of the orifice, the orifice cap having an exterior cylindrical bearing surface of smaller diameter than the diameter of the inner cylinder, an annular bleed groove formed in the cylindrical bearing surface, at least one bleed passage formed in the Orifice cap and communicating one of the hydraulic cham- 10 bers with the snubbing chamber, said bearing surface having a stop at either end thereof, a generally cylindrical snubber bearing of less axial length than the bearing surface and being retained by the bearing surface, said snubber bearing having its exterior surface in bearing engagement with the'outer cylinder, at least one pair of axially spaced metering ports of different size formed transversely of the bearing, the bearing having a longitudinal passage in communication with both of said spaced ports, the snubber bearing being axially movable to one position responsive to compression of the inner and outer cylinders for automatically positioning one of said metering ports in fluid ommunication with the bleed passage and being movable to another position upon extension of said inner and outer cylinders to position the other of said pairs of metering ports in fluid communi cation with said bleed passage whereby the rate of fluid flow through said bleed passage during compression of said cushioning unit will differ from the rate of fluid flow through the bleed passage during extension of said unit.

5. In a railway car having a cushioned underframe, a self-contained hydraulic-pneumatic cushioning unit comprising an outer cylinder having an end cap closing one end thereof, a metering pin fixed to the end cap and extending along the axis of the cylinder, an inner cylinder received in concentric spaced relation within the outer cylinder and defining a snubbing chamber therebetween, the other end of the outer cylinder being in sealing relation with the inner cylinder, an Orifice cap closing the inner end of the inner cylinder and having a metering orifice formed centrally thereof and adapted to receive the metering pin for varying the size of the orifice, the orifice ca-p having an exterior cylindrical bearing surface of smaller diameter than the diameter of the inner cylinder, an annular bleed groove formed in the cylindrical bearing surface, at least one bleed passage formed in the orifice cap and communicating the inner one of the hydraulic chambers with the snubbing chamber, said bearing surface having a stop at either end thereof, a generally cylindrical snubber bearing of less axial length than the bearing surface and being retained by the bearing surface, said snubber bearing having its exterior surface in bearing engagement with the outer cylinder, at least one pair of axially spaced metering ports of different size formed transversely of the bearing, the bearing having a longitudinal passage in communication with both of said spaced ports, the snubber bearing being axially movable to one position responsive to compression of the inner and outer cylinders for automatically positioning one of said metering ports in fluid communication with the bleed passage to allow relatively unrestricted flow of fluid through said bleed passage into said snubbing chamber and being movable to a second position during extension of said inner and outer cylinders to position another of said metering ports in fluid communication With said bleed passage to provide a relatively restricted flow of fluid therethrough.

6. A self-contained hydraulic-pneumatic cushion unit comprising an inner cylinder, an outer cylinder telescopically receivng the inner cylinder and defining therewith a variable volume outer hydraulic chamber, means dividing the inner. cylinder into a variable volume inner hydraulic chamber and a variable pneumatic chamber, a variable volume hydraulic. snubber chamber defined between the inner and outer cylinders and being in fluid communication with the inner chamber, hydraulic fluid filling the inner and outer hydraulic chambers and the snubber chamber, a compressible fluid filling the pneumatic chamber, means defining fluid communication between the inner and outer hydraulic chambers, said inner cylinder having a cylindrical bearing surface having stop means at either axial end thereof, a bearing disposed between said inner and outer cylinders said bearing slidably interfitting with said bearing surface and being axially movable relative to the bearing surface by said hydraulic fluid upon compression and extension of said cushioning unit, at least one bleed passage formed in the inner cylinder between the snubber chamber and inner chamber and opening into the snubber chamber on said bearing surface, said bearing having at least one series of axially spaced metering orifices of different size, during the compression stroke of the cushioning unit the bearing being movable by said hydraulic fluid to a position aligning the larger of the orifices with said bleed passage and during the extension stroke the bearing being movable by said hydraulic fluid to a position aligning the 12 smaller of the orifices With the bleed passage whereby the flow of hydraulic fluid from the snubber passage will be retarded to prevent rapid extension of the cushion unit. References Cited UNITED STATES PATENTS 10 ARTHUR A. LA POINT, Primary Examiner.

D. E. HOFFMAN, Assistant Examiner. 

1. A HYDRAULIC-PNEUMATIC CUSHION UNIT COMPRISING INNER AND OUTER TELESCOPED CYLINDERS DEFINING AN OUTER VARIABLE HYDRAULIC CHAMBER, SAID CYLINDERS DEFINING A SNUBBING CHAMBER THEREBETWEEN, THE INNER CYLINDER BEING CLOSED AT EACH END THEREOF, A FLOATING PISTON DISPOSED WITHIN THE INNER CYLINDER AND DIVIDING THE SAME INTO A PNEUMATIC CHAMBER AND AN INNER HYDRAULIC CHAMBER, A COMPRESSIBLE FLUID FILLING THE PNEUMATIC CHAMBER AND AN INCOMPRESSIBLE FLUID FILLING THE INNER HYDRAULIC CHAMBER, THE OUTER HYDRAULIC CHAMBER AND THE SNUBBING CHAMBER, ONE END OF THE INNER CYLINDER HAVING A METERING ORIFICE, THE OUTER CYLINDER BEING CLOSED AT ONE END THEREOF, A METERING PIN CARRIED BY THE CLOSED END OF THE OUTER CYLINDER AND ADAPTED TO EXTEND THROUGH THE METERING ORIFICE TO CONNTROL THE SIZE OF THE SAME, SAID INNER CYLINDER HAVING MEANS DEFINING A BEARING SURFACE HAVING A BEARING STOP AT EITHER END THEREOF, A SNUBBER BEARING SLIDABLY RECEIVED ON THE BEARING SURFACE AND BEING IN BEARING ENGAGEMENT WITH THE OUTER CYLINDER, BLEED PASSAGE MEANS IN SAID INNER CYLINDER ESTABLISHING FLUID COMMUNICATION BETWEEN THE HYDRAULIC CHAMBER AND THE SNUBBING CHAMBER, THE SNUBBER BEARING HAVING A PLURALITY OF DIFFERENT SIZED ORIFICES THEREIN, EACH WHICH COMMUNICATES WITH SAID BLEED PASSAGE AT DIFFERENT POSITIONS OF SAID SNUBBER BEARING RELATIVE TO SAID BEARING SURFACE TO ALLOW A PREDETERMINED RATE OF HYDRAULIC FLUID FLOW IN ONE DIRECTION THROUGH THE FLUID COMMUNICATION, AND A LESSER RATE OF FLUID FLOW IN THE OPPOSITE DIRECTION, SAID SNUBBER BEARING BEING HYDROSTATICALLY BALANCED TO PREVENT RADIAL STRESSING OF THE SAME BY THE HYDRAULIC FLUID. 